Both “Fuzz with dust” and “Dunes” contain the following rule as “subrules”: replace a cell’s value by the successor (mod N) of the average of the values of the von Neumann neighbours. How does this rule look on its own?

The answer is that it produces growing fluorescent cells on a folder-containing background:

The fluorescence becomes apparent when the background darkens, as it does cyclically:

A less zoomed-in picture (with a different colour scheme):

With the “Rainbow” colour scheme, the illusion of fluorescence disappears, but the images are still very pleasant: